This application is the national phase under 35 U.S.C. xc2xa7371 of PCT International Application No. PCT/AU98/00784 which has an International filing date of Sep. 21, 1998, which designated the United States of America.
This invention relates to an actuator enabling adjustment of a flexible line, cable, rope or the like.
The device of the invention is suitable for generating tension in a flexible line, such as a cable, rope or the like. However, it also is suitable for generating a pulling force, such as to adjust the position of a member, with the force being transmitted by such flexible line. In one embodiment, the actuator of the invention comprises a component of an adjustable headrest for a seat, such as a vehicle seat. In part, the actuator is described herein with reference to that application. However, it is to be understood that the actuator of the invention is well suited for use in a wide variety of other applications.
The present invention provides an actuator for enabling adjustment of a flexible line, wherein the actuator includes a screw threaded spindle and a co-operatively engaging threaded adjustment member which comprises a nut in having an internal screw thread by which it is in screw threaded engagement with an external screw thread of the spindle, and wherein the adjustment member is rotatable relative to the spindle so as to cause axial movement of the spindle. At one end of the spindle there is mounted thereon a turning block or pulley which is rotatable on an axis which extends transversely with respect to the axis of the spindle whereby a flexible line such as a cable, rope or the like can be retained in relation to the spindle by being passed around the turning block or pulley.
In one arrangement, the actuator includes a body or housing in which the spindle and the adjustment member are provided. The spindle may be extendable from the housing and, in that case, the turning block or roller may be located exteriorly of the body or housing during at least part of a range of axial movement for the spindle. However, it is preferred that the spindle is not extendable from the housing and that, throughout the range of axial movement for the spindle, the turning block or pulley also is within the body or housing.
The housing is preferably adapted to restrain the spindle against rotation as it is moved axially with rotation of the adjustment member. For this purpose the housing may define a groove or guideway which extends parallel to the axis of the spindle, with a portion of the spindle locating in the groove or guide way. Alternatively, the spindle may define a groove or guideway which extends parallel to the spindle axis, with a projecting portion of the housing being received therein.
The adjustment member is a nut in that it has an internal thread by which it is in threaded engagement with an external thread of the spindle. The nut most preferably is such that, with its rotation, the nut is able to move along that axis as the spindle moves axially relative to the nut. Thus, the nut most preferably is externally threaded and is in threaded engagement with an internal thread defined by the housing, with the external thread of the nut being of opposite hand to its internal thread. In that arrangement, rotation of the nut and, hence, axial movement of the spindle, can be achieved manually or by a motorised drive.
In a mechanical arrangement, there may be a knob or handle journalled on or in the housing, with the knob engaged with the nut whereby the nut is rotatable with the knob. The engagement may be such that the nut is axially adjustable relative to the knob as it rotates with the knob. In one arrangement the engagement is by respective splines extending parallel to the axis of the spindle such that manual rotation of the knob causes rotation of the nut while enabling axial movement of the nut relative to the knob. With an arrangement having a motorised drive, there may be for example a similar splined engagement between the nut and a rotatable output member of a drive motor.
In an embodiment of the actuator of the invention which is suitable for use with or in an adjustable headrest for a vehicle seat (herein referred to as xe2x80x9cthe headrest embodimentxe2x80x9d), the actuator is of elongate form in the direction of the spindle axis. The actuator is adapted at a first end to receive a flexible line by which the headrest is adjustable, while manual or powered drive is able to be provided at its second end to operate the actuator. For ease of further description, the first and second ends are referred to as the cable end and the drive end, respectively, while the corresponding ends of the housing, the spindle and the adjustment member are similarly distinguished.
In the headrest embodiment, the housing overall has a hollow cylindrical form which is open at its drive end, but preferably is partially closed at its cable end. Over a portion of its internal surface nearer to the drive end, the cable defines an internal screw thread. The nut is of cylindrical form and over a portion of its length extending from its cable end, the nut defines an internal screw thread. Over a part of its length from the drive end, the nut defines an external screw thread by which it is engaged with the internal thread of the housing, while the external thread is of opposite hand to the internal thread of the nut. Also the nut is recessed axially inwardly from its drive end to define internal, axially extending splines by which drive is able to be supplied to the nut to cause its rotation relative to the housing.
The spindle of the headrest embodiment, from its drive end, has a main part in the form of an externally screw-threaded shank. The shank is received axially inwardly from the cable end of the nut by screw threaded engagement between the internal thread of the nut and the external thread of the spindle. At its cable end, the spindle is of bifurcated form to provide a pair of tabs which extend longitudinally from the shank part and which define a gap therebetween. The tabs are symmetrically disposed on opposite sides of the axis of the spindle shank, with the tabs parallel and facing each other. The spindle has a pulley which is mounted between the tabs, and which is rotatable on a pin extending through aligned holes in the tabs. The pulley has a diameter which exceeds the lateral dimensions of the spindle, while the pin is perpendicular to and intersects the spindle axis, such that a respective segment of the pulley is exposed each side of the spindle as viewed along the pin axis.
In the headrest embodiment, rotation of the nut in the housing enables the nut to advance or retract axially in housing between limits set by their respective threads in engagement. As the internal thread by which the nut is engaged with the spindle is of opposite hand to the external thread by which the nut is engaged with the thread of the housing, the spindle is able to advance from or retract into the nut as the nut respectively advances or retracts in the housing. Thus, the spindle is able to move axially with respect to the housing by a distance which is the sum of the distances through which the nut moves relative to the housing and the spindle moves relative to the nut.
With movement of the spindle between fully retracted and fully advanced positions, the pulley transverses a longitudinal portion of the housing in which the housing is unthreaded. However, in that portion, there is means for restraining the spindle against rotation relative to the housing as the spindle moves axially. This restraint is provided by the segment of the pulley exposed at each side of the spindle being located in a respective longitudinal groove or slot defined in or through the housing. Also, while the housing preferably is partly closed at the cable end, there is a continuation of each of these grooves or slots such that a flexible cable is able to be inserted through the cable end of the housing, along one groove or slot, and pass around the pulley and then back along the other groove or slot.
As indicated above, drive to the actuator of the headrest embodiment is able to be supplied by means of axially extending internal splines defined within the drive end of the nut. To provide drive, the embodiment includes a knob mounted at the drive end of the housing by which the nut is manually rotatable. The knob has a hand-grip portion and, projecting from this, a stem which defines external splines. The stem is received axially within the recessed drive end of the nut such that the respective splines mesh and the nut is able to be rotated by manual rotation of the knob. Also, the knob has a cylindrical skirt portion which is received coaxially around the drive end of the housing with the stem received in the nut; with the knob being releasably retained on the housing by the skirt having an inner circumferential bead by which it is a snap-fit over external, raised formations on the housing.
The housing of the actuator of the headrest embodiment preferably is of integral construction, rather than of two longitudinally split halves. To enable this and a compact construction, each segment of the pulley which is exposed at a respective side of the spindle locates in a groove defined through the housing. The arrangement is such that the pulley, prior to it being mounted between the tabs of the spindle, is able to be inserted through one of the grooves of the housing. Thus, with the spindle retracted into the nut, but without the pulley and the pin fitted to the spindle, the nut and spindle are inserted into the drive end of the housing, with the tabs of the spindle leading. When the leading end of the internal thread of the nut contacts the trailing end of the thread of the housing, the nut is rotated to initiate threaded engagement between these threads. The rotation is continued to a limited extent until the spindle and nut reach a position in which the gap defined between the tabs is aligned with each of the grooves defined by the housing and the holes in the tabs are aligned with a hole through at least one of diametrically opposed sides of the housing. The pulley then is able to be inserted through one of the grooves in the housing to a position between the tabs, after which the pin is able to be inserted through the hole in the housing, the hole in the nearer tab and then through the pulley and the other tab so as to rotatably mount the pulley in relation to the spindle.
As the nut is rotated to achieve initial threaded engagement between it and the housing, the spindle rotates with the nut in the absence of any factor causing relative rotation between the spindle and nut. However, with the pulley mounted in relation to the spindle, each segment of the pulley is located in a respective groove of the housing. This restrains the spindle against rotation relative to the housing and thereby enables relative rotation between the spindle and nut.
A flexible cable is positioned in relation to the spindle as detailed above. To achieve this, the cable can be inserted through the housing, so as to pass around the pulley, after the pulley has been mounted in relation to the spindle but preferably after the spindle and nut have been at least partially advanced from their fully retracted positions. Alternatively, the cable can be inserted through the housing prior to the pulley being inserted into the housing, with the pulley after its insertion and securement by the pin trapping a part of the cable therearound.
In use of the actuator of the headrest embodiment, one end of the cable is secured, either to the housing at the cable end thereof or to a fixed component such as a fixed part of a headrest. The other end of the cable is secured to a movable component of the headrest. The arrangement may be such that, with the nut and spindle in their advanced positions, the length of cable is just sufficient to enable biasing means to move the moveable component of the headrest to one of two positions between which the movable component is adjustable relative to the first component. As the knob is rotated to retract the nut and spindles, tension in the cable is increased and the cable is caused to advance around the pulley, with the moveable component being adjusted to or towards its other position.
The components of the actuator can be made of a number of materials. In some applications, it can be desirable for at least some components to be of a suitable metal such as aluminium, brass, copper, magnesium, zinc or steel. However, for other applications it is beneficial to have components made of a suitable plastics material, such as by injection moulding from a thermoplastic material.
An adjustable headrest with which an actuator according to the invention is able to be used, may include a core structure which can be mounted on a guide system for up and down movement relative to an associated seat backrest, and which has relatively movable first and second sections. In one preferred arrangement, the first section is an inner section which is mounted on the guide system for relative up and down movement, and the second, outer section is connected to the inner section for relative movement about a pivot axis such as to permit fore and aft adjustment of the headrest position. In another embodiment, the first section is mounted on the guide system for relative up and down movement, and the second section is connected to the first section for relative linear movement such as to permit fore and aft adjustment of the headrest.
The headrest includes a drive system which controls up and down adjustment or fore and aft adjustment, with the drive system including the actuator of the invention and at least one flexible cable through which the actuator controls the relevant adjustment of the headrest. The arrangement is preferably such that there are two such drive systems each respectively controlling up and down adjustment and fore and aft adjustment. In that arrangement the headrest can be readily adapted for either two-way adjustment or four-way adjustment. In the former case, one of the actuators is selected as the operable actuator, whereas in the latter case both actuators are operable. It is further preferred that each of the two drive systems is readily adaptable to either manual operation or power operation.
In one particular embodiment of the invention the headrest is adapted for use with a mounting system including two laterally spaced support posts which are secured to the seat backrest and project beyond the upper edge of that backrest. The headrest core structure may be mounted on both of the posts for relative sliding movement in the axial direction of the posts. A cross member may extend between and be secured to the upper end portion of each of the posts, in which case the elevation drive system of the headrest may extend between that cross member and the first section of the headrest core structure. By way of example, first biasing means may act between the cross member and the first section so as to urge the core structure to move down the support posts away from the cross member, in which case the flexible cable of the elevation drive system is operable to pull the core structure upwards against the influence of the first biasing means. Second biasing means may urge the second section of the core structure in a rearward direction relative to the inner section, in which case the flexible cable of the fore and aft drive system is operable to pull the second section forward against the bias.
The actuator or each actuator, may be mounted on the headrest, or it may be mounted on the backrest or at some other convenient location remote from the headrest.
It will be convenient to hereinafter describe the invention in greater detail by reference to the accompanying drawings which show example embodiments of the invention. The particularity of those drawings and the related detailed description is not to be understood as superseding the broad description of the invention given in the preceding part of this specification.